The alleged offenses happened two years ago but were only made public this week after local media came across a Facebook site, which named and "slut-shamed" girls the boys had allegedly attacked.

Her face and voice disguised, one of the alleged victims told 3 News: "I just kept blacking out 'cause I had drunken too much... You could say I got raped. I had sex with three guys at one time."

The alleged offenders -- a group of then school-aged boys -- call themselves the "Roast Busters." Until this week police say they'd been boasting of their exploits on a number of websites, including Ask.fm and Twitter, as well as the Facebook site which has been shut down.

In a video posted to YouTube, two boys made no attempt to hide their faces as they told the camera: "We don't choose the roast, the roast chooses us ... They know what we're like; they know what they're in for."

Prime Minister John Key described the boys' comments as "extremely disturbing and disgusting," but appeared to sympathize with police who say they're unable to file charges until one of the alleged victims makes a formal statement. And despite one of the girls appearing on TV, police say no one is willing as of yet to file an official complaint.

Police say they have been actively monitoring the group since the alleged offenses were committed in 2011.

They say the Facebook site appeared for the first time for a couple of months earlier this year, and reappeared a few weeks ago. Officers had been monitoring the site for enough evidence to warrant an arrest but were unable to find any before 3 News informed Facebook of its existence and had the page shut down.

Police say they've spoken with the boys but they have not admitted anything that constitutes a criminal offense.

"We have interviewed two of the boys [on Monday] again but we're still not in a position to take immediate action," Waitemata police District Commander Superintendent Bill Searle told CNN.

"The online claims themselves are not enough to warrant a prosecution. They might be morally inappropriate and unacceptable to us but we have to deal with evidence that would be admissible in a court of law and we haven't got to that stage yet," he said.

Searle refuted allegations that no action had been taken because one of the boys is an officer's son. The other is said to be the son of a Hollywood actor, according to local press reports.

"NZ Police take any allegations of criminal offending by any of its officers or their families extremely seriously and recent cases have highlighted that police will not hesitate to thoroughly investigate staff facing allegations of a criminal nature and will put them before the court if there is a case to answer," Searle said in a statement.

Police declined to confirm how many boys were involved in "Roast Busters," but said the two ringleaders led a "core group," as well as "an associated group." The boys were attending at least two different schools at the time the alleged offenses were committed but all have since graduated, police said. It's believed they're now around 17 to 18 years old.

Police also declined to confirm how many victims were involved but said it was "a relatively small number" and confirmed at least one had attempted suicide.

"There's no doubt they've been severely traumatized by their involvement," Searle said. Police have been counseling the girls since the alleged offense was reported but have yet to convince any to come forward and file a formal complaint.

"We understand it's a very difficult situation for them -- and it would be a very difficult situation for them if they were to come forward for a court case," Searle said.

The case has inspired a number of online vigilante groups. Police said they are monitoring online death threats made against the boys and that action would be taken if "anybody oversteps the mark."

On 3 News on Tuesday evening, a group of five girls aged between 16 and 19 defended the boys as "good guys."

"People know that they are Roast Busters and they go hang out with them and do stuff [... ] I don't think they're rapists, they're actually pretty cool dudes," one said.

Asked whether "drunken group sex" was normal behavior, another said: "It's normal in west Auckland... Not for everybody though it's just the young ones 13 to 15 year olds -- that's what they do."

New Zealand Police Minister Anne Tolley told CNN she was satisfied that "police are doing everything in their powers to resolve this case."

Efforts are also underway to tighten the laws on cyber bullying in New Zealand.

On Tuesday, a new bill was introduced to parliament which proposes a three-year prison sentence for posting material online with an "intent to cause harm" as well as other measures to stop cyber bullying.

"No longer is bullying confined to the classroom or playground -- the digital age has meant tormenters can harass their target anywhere, at any time and the trails of abuse remain in cyberspace forever," Justice Minister Judith Collins said in a statement.

"The Harmful Digital Communications Bill sends a strong message to those who continue to harass and harm others online -- time's up."